IAI Accepts, published online ahead of print on 2 September 2008

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Infect. Immun. doi:10.1128/IAI.01615-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

INTESTINAL ADHERENCE OF VIBRIO CHOLERAE INVOLVES A COORDINATED INTERACTION BETWEEN COLONIZATION FACTOR GbpA AND MUCIN

RUDRA BHOWMICK, ABHISEK GHOSAL, BHABATOSH DAS, HEMANTA KOLEY, DHIRA RANI SAHA, SANDIPAN GANGULY, RANJAN K. NANDY, RUPAK K. BHADRA, and NABENDU SEKHAR CHATTERJEE^*

National Institute of Cholera & Enteric Diseases, Kolkata, India; Infectious Diseases & Immunology Division, Indian Institute of Chemical Biology, Kolkata, India

^* To whom correspondence should be addressed. Email: chatterjeens{at}icmr.org.in; nschatterjee@rediffmail.com.

The chitin-binding protein GbpA of Vibrio cholerae has been recently described as a common adherence factor for chitin and intestinal surface. Using an isogenic in-frame gbpA deletion mutant, we first show that V. cholerae O1 El Tor interacts with mouse intestinal mucus quickly, using GbpA in a specific manner. The gbpA mutant strain showed significant decrease in intestinal adherence, leading to less colonization and fluid accumulation in a mouse in vivo model. Purified recombinant GbpA (rGbpA) specifically bound to N-acetyl-D-glucosamine residues of intestinal mucin in a dose-dependent, saturable manner with a K_d of 11.2 µM. Histopathology results from infected mouse intestine indicated that GbpA binding resulted in a time-dependent increase in mucus secretion. We found that rGbpA increased the production of intestinal secretory mucins (MUC2, MUC3 and MUC5AC) in HT-29 cells through upregulation of corresponding genes. The upregulation of MUC2 and MUC5AC genes was dependent on NF-B nuclear translocation. Interestingly, mucin could also increase GbpA expression in V. cholerae in a dose-dependent manner. Thus, we propose that there is a coordinated interaction between GbpA and mucin to up-regulate each other in a cooperative manner, leading to increased levels of expression of both of these interactive factors, ultimately allowing successful intestinal colonization and pathogenesis by V. cholerae.